1. Field of the Invention
The present invention relates to a method for measuring a transistor in which an oxide semiconductor is used for a semiconductor layer.
2. Description of the Related Art
In recent years, metal oxides having semiconductor characteristics (hereinafter, referred to as oxide semiconductors) have attracted attention. The metal oxides having semiconductor characteristics can be used for transistors. For example, in Patent Documents 1 to 3, thin film transistors in which an amorphous oxide (an oxide semiconductor) with an electron carrier concentration of lower than 1018/cm3 is used for a semiconductor layer is disclosed.
A transistor when used in many types of products preferably has high reliability. Therefore, it is necessary to know characteristics of a transistor in an environment of practical usage.
As a method for examining the characteristics of a transistor, a bias-temperature stress test (hereinafter, also referred to as a BT test) is known. As the condition for the BT test, a temperature, a bias condition, and the like are considered (Patent Document 4).